Tips to copyright your fiction or screenplay

Writers frequently ask me about how to protect their work, and here is my general advice:

The second you create something i.e. put words to paper, then you own the copyright to your work.

Ideas cannot be copyrighted. If you tell people, "I have this idea where a robot marries a woman!" That idea is not protected. However, you write it, and that story is yours. Does that mean people cannot write a story about a robot marrying a woman once you wrote yours? That's iffy. If they have a unique take, then that may be allowed. You'd have to talk to a lawyer for specifics. The main thing you should be concerned with then is your execution, not your idea, because if someone steals your execution then that is an actual legal problem.

If you write a story and someone steals lines/paragraphs then that is plagiarism and a violation of your copyright. This is rare, yet it happens, so even though you own the copyright, what are further ways for you to protect yourself from this theft?